OPHIUBANS OP UNITED STATES NATIONAL MUSEUM. 57 



smaller. There is not the slightest indication of primarj' plates. The radial shields 

 are large, rather elongated, three times longer than wide, preserving about the same 

 width in their whole length, and their distal and pro.ximal ends are rounded. The 

 shields of the same pair are not much divergent; distally they are close to each other 

 or in contact, and they are separated proximally at first by one or two successive 

 elongated plates and then by some smaller plates. 



The under face of the disk is covered with small, rounded plates, rather loosely 

 put together, and transparent, under which may be seen the underh-ing tissues 

 which are of a dark color. These plates do not form a very hard covering and they 

 differ from the upper plates, with which they have no continuity at the margin of 

 the disk; but still, they completely cover the under face and extend up to the 

 mouth shields. 



The mouth shields are rather large, notably longer than wide, their shapes 

 being almost lanceolate, but their proximal angle is strongly obtuse and rounded 

 and even sometimes semicircular; the lateral angles also are very much roimded 

 and are succeeded by two slightly excavated and convergent lateral edges, which 

 meet at angles which are also rounded, and a small dLstal side, transverse and almost 

 straight. The adoral plates are somewhat small, triangular, with the three sides 

 concave; the oral margin especially is excavated by the tentacular oral pore which 

 is very large; these plates are hardly contiguous on the median iuterradial line by 

 their internal ends which are rounded. The middle-sized oral plates are higher 

 than wide; thej' are terminated by a large, rounded, and obtuse papilla. The 

 external oral papilla located at the meeting point of th6 oral and adoral plates is little 

 developed, conical, with a roimded end, and is obliquely erect. On a higher level is 

 seen, as usual, a small papilla equal in size to the foregoing, but thinner and more 

 pointed. 



Tlie upper brachial plates are small, almost circular at the base of the arms, 

 with a proximal edge slightly excavated. They afterwards become oval in shape, 

 transversely, and a little wider than long, with the distal side more convex than the 

 proximal one. They are all in contact. On the upper median line extends a very 

 light yello^^^sh stripe, which can hardly be distinguished on the specimen in alcohol. 



The first under brachial plate is small, narrowed in its distal part, which is 

 compressed between the ends of the adjacent adoral plates and widened proxunally. 

 The other plates remain rather small. 'Hie second one is quadrangular, somewhat 

 longer than wide, with its proximal margin widened and slightly notched, while the 

 distal edge is smaller and roimded. The succeeding plates are quadrangular, with 

 straight edges and rounded corners; they are hardh' longer than wide and are all ia 

 contact. 



The side plates, Uttle protruding, extend fairly over the upper face of the arms. 

 Each of them carries seven spines, the length of which slightly decreases from the 

 first ventral one, which is equal to the article, down to the last dorsal. The first is 

 cylindrical, rather thick, and has a very rough surface; its roimded end bears very 

 fine denticulations which are more or less conspicuous. The other spines are 

 flattened and their surfaces are always very rough. Tlie second ventral spine is 

 generally bihamuled; however, the two hooks which are at its extremity, and one 



